Polygenic Factors

Heritability and Risk of Inheritance in Multifactorial Disorders. Heritability may be defined as the additive proportion of total phenotypic variance in a polygenic trait attributable to genetic variation in a population. The values of heritability estimates can range from 0% to 100%. Heritability is a function of genetic factors, environmental factors, and the interaction of genetic and environmental factors. Simple Mendelian traits have a heritability of 100%. Diseases with a heri-tability of less than 100% are inevitably controversial, such as those listed in the previous paragraph.

Other non-Mendelian mechanisms of clinical significance have been recently re-evaluated in terms of new molecular knowledge (the "new genetics"), but are not considered in this review (Anonymous, 1997a, 1997b). These mechanisms include: X inactivation, dosage compensation, epistasis, ectopic recombination, meiotic drive, position effects, microdeletions, other contiguous gene syndromes, chimerism, pleiotrophic homeotic mutations, slippage, and germline mosaicism.

100 Health Tips

100 Health Tips

Breakfast is the most vital meal. It should not be missed in order to refuel your body from functional metabolic changes during long hours of sleep. It is best to include carbohydrates, fats and proteins for an ideal nutrition such as combinations of fresh fruits, bread toast and breakfast cereals with milk. Learn even more tips like these within this health tips guide.

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